Study Update Water Quality Modeling Lake Creek Evaluate summer - - PowerPoint PPT Presentation

Study Update Water Quality Modeling

Lake Creek

• Evaluate summer water temperature in

Lake Creek downstream of Packwood Lake.

• Compare temperatures for existing to

without Project and natural conditions

• Evaluate Project temperature loading to

Cowlitz River

• Evaluate relative to water quality

standards for temperature

QUAL2Kw Model

• Widely applied by WDOE
• One dimensional model
• Steady state hydraulics. Non-uniform,

steady flow is simulated.

• Diel heat budget.
• Heat and mass inputs. Point and non-

point loads and abstractions are simulated

Model Setup

• Bathymetry: IFIM X-Secs; Depth and width as a

function of flow

• Vegetation data (available at

http://www.fs.fed.us/gpnf/forest-research/gis/ applied to WDOE Shade Model

• Hydrology: Existing, 7Q2, 7Q10 flows

– Without Project 1912 – 1962 gage data – Accretion distributed by basin area – Hyporheic option not used

Model Setup

• Existing shade approximates natural condition from lake outlet to

USFS boundary

Longitudinal Effective Shade Profile 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Longitudinal Distance (meters) starting at Drop Sturcture Fraction of potential solar radiation blocked by topography and vegetation (%)

Model Setup

• Climate data available at Lake and at

Packwood powerhouse

• NCDC Coop station at Packwood provided

supplemental data and estimating median and extreme climate conditions

Median climate 26.0 Aug 21 2005 10% exceedance climate 32.78 Aug 14 2005 10% exceedance climate 33.89 Aug 12 2004 Median climate 26.1 Aug 5 2004 Rationale Air Temp Max (oC) Date

Modeling dates for Lake Creek

Model Calibration

• Compare measured to predicted

temperature at 0.5 km and 7.9 km downstream of lake

• Model was primarily sensitive to

groundwater (inflow rate and temperature)

Model only slightly sensitive to riparian shade

August 5 2004 (7Q2 flow and average climate conditions)

5 10 15 20 25 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00

Distance Downstream of Lake (km)

Maximum Daily Water Temperature (C)

Without Project Without Project No riparian shade

Model Calibration

• Predicted Maximum daily -0.24C cooler, on average, than measured
• Predicted Mean daily 0.4C warmer, on average, than measured
• Predicted Minimum within 0.1C of measured
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5 10 15 20 25 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 Distance Downstream of Lake (km)

Maximum Daily Water Temperature (C)

with Project Without Project 7Q10 7Q2

August 14, 2005

10% exceedance climate

7DADMax

• Modeled with and without Project for August 15-

21, 2004 (highest on record below drop structure)

• Natural inflow to lake applied: 15% above 7Q10
• utflow
• Calibration: Absolute mean error at Rkm 0.5=

0.22C and at Rkm 7.9 = 0.16C

• 7DADMax without Project = 19.27C
• 7DADMax existing = 14.16C
• 7DADMax tailrace lower end = 21.25C
• Combined flow weighted average 7DADMax for

Lake Creek at mouth and lower tailrace =19.92C

Downstream Temperature Effect

• Mass Balance/Energy analysis
• Lake Creek flow and tailrace flow
• Analyzed for 7Q2 and 7Q10 flows
• Assumed full instantaneous mixing without

accounting for tailrace slough

• No significant temperature effect on

summer Cowlitz River temperatures

Summary

• Temperature just downstream of lake is function
• f lake outflow temperature
• Temperature near mouth is a function of cool

groundwater inflow

• Effect of Project is cooler summer temperatures

in Lake Creek

• Flow weighted average 7DADMax (Lake Creek

+ tailrace) slightly warmer than 7DADMax for natural condition in Lake Creek

• No downstream temperature effect for Cowlitz R.
• Water quality modeling for lake is in progress